Chemotherapy and radiotherapy cause severe damages to the immune system of cancer patients. Although chemotherapy-induced neutropenia can be alleviated with recombinant granulocyte colony-stimulating factor, therapeutic options to treat damages caused by standard cancer therapy are limited, which underscores the importance of the development of new drugs to improve the quality of life (QOL) of cancer patients. Our recent study indicates that a series of diacylglyceryl glycosides (DGGs) are potent immunostimulants in an oriental herbal formulation called Juzen-taiho-to (JTT), which is clinically used to rebuild the immune system of cancer patients in Japan. The proposed study has two aims; namely, (i) structural elucidation of the series of DGGs in JTT and characterization of the structure-activity relationship of these compounds. Once the structural requirements for the immunostimulation by DGGs are clarified, it would become possible to fully explore their therapeutic potential with rationally designed new immunostimulants based on the simple DGG framework. The proposed research, therefore, opens an exciting possibility that QOL of cancer patients can be improved with a cocktail of chemically defined, orally available small molecules.